ANALYSIS OF THE HYPOGENE ALTERATION AND MINERALIZATION OF THE MOONLIGHT (IOCG) DEPOSIT, TAYLORSVILLE DISTRICT OF THE PLUMAS COUNTY COPPER BELT, CA

The Moonlight deposit, located in the Plumas County Copper Belt, California, is an iron oxide copper-gold (IOCG) deposit hosted in the quartz monzonite of the Lights Creek Stock. Few studies have focused, in detail, on the Moonlight deposit, as there is little to no surface exposure. To characterize the mineralization and alteration of the deposit, detailed core logging and petrographic analysis was conducted on five drill cores. The five cores were chosen based on historical drill logs that detailed the length, grade of copper, location of core through the deposit, and quantity of remaining core. Holes 08-MN-16, 08-MN-19, and 08-MN-20 were drilled vertically and holes 06-MN-04 and 06-MN-11 were drilled at an angle approximately 45 degrees. The five cores span the length of the Moonlight deposit and all have zones of high (>0.25 wt.%) copper assay. Some of these peaks correlate to sections of hypogene mineralization/alteration while others are a combination of hypogene and supergene mineralization/alteration. Hypogene copper minerals include chalcopyrite and bornite, but not all of the five cores contain these minerals. In hole 08-MN-19 bornite and chalcocite are the only copper sulfides observed. From 10-40 ft., four cores have disseminated and veined chalcopyrite and bornite. In the four cores, the dark colored veins contain tourmaline, quartz, and fine-grained copper sulfides (chalcopyrite, bornite, and copper-arsenic) and are approximately 0.03-0.1mm in size and are oriented at 0-170 degrees. Disseminated chalcopyrite and bornite range in size from 0.05mm-2cm and are associated with tourmaline, specular hematite, and epidote/chlorite. Chalcopyrite is more prevalent than bornite and is typically associated with pyrite. The observed suite of mineral associations in the Moonlight deposit facilitates a better understanding of the primary mineralization and alteration of IOCG deposits.